title: High irradiance increases NH(4)(+) tolerance in Pisum sativum: Higher carbon and energy availability improve ion balance but not N assimilation.
abstract: The widespread use of NO(3)(-) fertilization has had a major ecological impact. NH(4)(+) nutrition may help to reduce this impact, although high NH(4)(+) concentrations are toxic for most plants. The underlying tolerance mechanisms are not yet fully understood, although they are thought to include the limitation of C, the disruption of ion homeostasis, and a wasteful NH(4)(+) influx/efflux cycle that carries an extra energetic cost for root cells. In this study, high irradiance (HI) was found to induce a notable tolerance to NH(4)(+) in the range 2.5-10mM in pea plants by inducing higher C availability, as shown by carbohydrate content. This capacity was accompanied by a general lower relative N content, indicating that tolerance is not achieved through higher net N assimilation on C-skeletons, and it was also not attributable to increased GS content or activity in roots or leaves. Moreover, HI plants showed higher ATP content and respiration rates. This extra energy availability is related to the internal NH(4)(+) content regulation (probably NH(4)(+) influx/efflux) and to an improvement of the cell ionic balance. The limited C availability at lower irradiance (LI) and high NH(4)(+) resulted in a series of metabolic imbalances, as reflected in a much higher organic acid content, thereby suggesting that the origin of the toxicity in plants cultured at high NH(4)(+) and LI is related to their inability to avoid large-scale accumulation of the NH(4)(+) ion.
authors.affiliation: Institute of Agrobiotechnology, Public University of Navarre-CSIC-Government of Navarre, Campus de Arrosadía, E-31006 Pamplona, Navarra, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Ariz
authors.forename: Ekhiñe
authors.initials: E
authors.lastname: Artola
authors.forename: Aaron Cabrera
authors.initials: AC
authors.lastname: Asensio
authors.forename: Saioa
authors.initials: S
authors.lastname: Cruchaga
authors.forename: Pedro María
authors.initials: PM
authors.lastname: Aparicio-Tejo
authors.forename: Jose Fernando
authors.initials: JF
authors.lastname: Moran
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects* / Q000528:radiation effects; D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000645:Ammonium Sulfate / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D002241:Carbohydrates / Q000032:analysis; D002244:Carbon / Q000032:analysis / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D018532:Pisum sativum / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D017785:Photons; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects* / Q000528:radiation effects
chemical_list: D002241:Carbohydrates; D009566:Nitrates; D002244:Carbon; D000255:Adenosine Triphosphate; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen; D000645:Ammonium Sulfate